Miss-distance indicator



July 15, 1958 w. c. WARD ET AL 2,843,028

MISS-DISTANCE INDICATOR Filed March 11, 1955 2 Sheets-Sheet 1 2e '0 FIRE E CAMERA Y CONTROL TRIGGER I8 COMPUTER swn- 1 M4 SOLENOID 2o /16 TIMING A CAMERA DEVICE FIRING RELAY I RELAY INVENTORS WILLIAM C. WARD NEWTON E. WARD BY r4 )If0061/ ATTORN'EYS July 15, 1958 w. c. WARD ETAL v 2,843,028

MISS-DISTANCE INDICATOR Filed March 11, 1955 2 Sheets-Sheet 2 INVENTORS WILLIAM C. WARD NEWTON E. WARD 7 2.. ATTORNEYS 9 tacks can bemade.

a 3 2,843,028 r MISS-DISTANCE INDICATOR William C. 'Ward and Newton E. Ward, China Lake,

, Calif assignors to the United States of America as represented by the Secretary of the Navy Application Marchll, 1955, Serial No.'493,840

v I 3 Claims. or. 95-12)" .(Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any. royalties thereon or therefor.

This invention relates to a miss-distance indicator, a

training aid for increasing the marksmanship of pilots of fighter aircraft, in particular.

, The performance I of military aircraft has increased tremendously since the end of World War II. The; very high speeds of bothfi'ghter and bomber type aircraft has made it more difficult for" fighters to destroy bombers and/or other fighters,,because of the relatively small favorable speed differential of fighters over bombers which reduces theopp'ortuni ty of makingrepeated'passes at; a'bomber and limits the angles atwhich successful at- T counterbalancethese developments, there has been afstea dy improvement in the weapons provided fighters such, as. an increase in the size of, guns from .50 caliber machine guns to 20 millimeter cannon and in the use of air toair rockets ,in the place of guns or cannon. There have also been improvements in the fire control equipment provided the fighter pilot so that the probability of obtaininghits on the targetin a single attack' has been improved." i w w jMo'dern' aircraft fire control'systems include some form of'f a computer, generally. an analog computer, which is 7 provided with information such as the range from'the 2,843,028 Pat te Jul i 1 55 takes a considerable period of time, a of several hours, so that by the time the pilot knows how well, or poorly, he was shooting, he is likely to have forgotten what he did during the course of each attack. 1 Z

Themost desirable time to provide the pilot of a fighter aircraft with information as to the direction and magnitude of the errors with which the weapons hefired, may

' have missed the target, is as soon after the attack as posfighterto thetarget, the rate of change ofthe-rang e the" ammunitiotil ballistics, :the'. atmosphericv pressure, 1 the velocity of the attacking fighter,v and fighter acceleration,

and if rockets are bingfired, the" rocket burning time, ,the angle of attack-of the fighter, and its angleof skid. From the information'provided,the computer derives the proper 7 angle the attacking fighter mustleadfthe target :in order for the particularytypefof missilewhich is being fired to hit the target. In the process of solving the ballistic.e 'quation's-in order forf the missile to intercept thetarget, the

tiniefof flight, t,; iscomputed, and is usnall yfpresented as anelectricalsignal variation. Typically the signal variation m-ay'beindi'cated by magnitude variations of a D.-C. 7

Voltage; or; urrent .or by modulation of an A.-C. voltage 1f r rentfUIf I l Fighter. pilots are, trained to use such aifroraft fire controlsystemsfby' attacking suitable targets such as an object 7 whichi'istowed by anotheraircrafn or a free flying robot typetargetL Fighter planes in the past havebeen equipped with [gun cameras takepictures during the firing of tracer type ammunition at the target by the fighter air craft. ,From such pictures it is possible fo r. thegpilot tollear'n the. number of 4 hits -obtaine d in a given attack a orthemagnit eand directiongof the misses. ;When I a 1!; f ieli mist is being Per m h r l will i normally makejiiti rnerous attacks on thetargetiand after n s nsissi h s.amm ni ion t e willlandtk hei h I guncanlera isfihell ,developed and evaluated. 1 lt1$ 1m at he l nta d eva ua tqgnfth re t sible. When this is' done, the pilot will remember, the action he took during each attack and see the consequences. If this information is available before the second attack he can endeavor to eliminate the cause, or causes, of the previous errors and thus more rapidly and accurately improve his marksmanship.

It is, therefore, an object of this invention to provide a relatively simple and inexpensive device for providing the pilot of an aircraft with information as to the magnitude and direction of any error he may'have made in firing at a target during an attack while the pilot is still air-borne' It is a further object of this invention to provide the pilot of an aircraft with a picture which shows the direc-' tion and magnitude of such error as may have occurred while making an attack on a target within a matter of minutes after the attack is made. i V t It is a still further object of this invention to provide a pilot of an aircraft with a picture showing the direction and magnitude of the distance between the target and] the missiles fired at the. target atthe time the missiles are closest to the target. g V; Other objects and many of the attendant advantages of this invention will be readily appreciated as the same be:

come better understood by' reference to the following'de accompanying drawing wherein: f

Fig. '1 is a block diagram of the invention,

tailed description when considered in connection with the Fig.'-2 is a broken away view ofthefcockpit ofafighter v aircraft p p v p I Fig; 3' is a side elevation of a camera and itsmountfi V Fig. i4'is a schematic'diagram'of 'a timing device, and

Fig. 5 is anexample of the type of picture suppliedthe Referring nowtothe' drawings wherein like ier rneej I 5 characters designate like or corresponding parts'through time of flight t of the missile to the point wherethe missile Will intercept the target Voltage Vi} is applied tojthe.

' timing device 16. When the pilot presses trigger switchlES which isshown as being mounted on the 'controlstickof; the cockpit in Fig. 2,, firing relay 20 isenergized. Whenthis occurs, the timing device 16 becomesoperationaLandf at the time t, after triggerswitch 18 isfclosed, timing device V closest to the target. ,Camera 26 is of the type,"such.as the'l I i nned to the instrument panel 3 0 of aircraft 12b'y bracket; 2

1.6 energizes camera'relay '22. Camera relay 22 then energizes solenoid 24which is mounted beside camera 26? and operates the shutter mechanism of caniera'26to'iekpose the film in the camera at the timethe fired missiles are Land cameraf that' can produce a positive print within a relatively short time, i. .e.,. 60 seconds, 'after-t-he iieg'ati' isexposed. A

Camera 26 is-mounted thej c'ockpitof aircraft 'lfas seen inFig. 2 soas' to pointin the same direction that the armament of the aircraft is fired; Camera 26 is provided witha fairly wide anglelens 28 so that alignment 7 between the cameraiandthejarmament is not particularly:-

critical. Camera- 26 lS illustrated in Fig. ;2 .asybeing.

32. The particular location of camera 26 in the cockpit of aircraft 12 is not critical since camera 26 may be mounted in any suitable space where it has a reasonable field of 'view in-the direction the armament is fired and which place is accessible to the pilot so that he may operate camera 26 and obtain the picture shortly after the film has been exposed.

Fig. 4 isascliematic diagram of one form of timer 16. Voltage V from computer is applied from output terminal 14. of fire control computer 10 across resistor 34 of potentiometer 36. A portion of voltage V is picked off by arm 38 of potentiometer 36. This voltage, the input voltage to the timer V is applied to a conventional cathode follower 40. The output of cathode follower 40 is applied through a single pole double throw switch 42 of firing relay 20 to the input terminal 44 of a high gain D. C. amplifier 46. Amplifier 46, as the result of positive feedback, has substantially an infinite gain over its region of operation. In order to reduce the gain of amplifier 46, negative feedback is obtained by connecting a portion of the output of amplifier 46 at output terminal 48, through the single pole double throw switch 50 of firing relay 2t) and resistor 52 to the input terminal 44 of amplifier 46. Condenser 54 is con nected between the output terminal 48 and input terminal 44 and shunts negative feedback resistor 52 when switch 50 is in the position illustrated in Fig. 4. Output terminal 48 is also connected to the control grid of thyratron 56, and the coil 58 of camera relay 22 is connected in the plate circuit of thyratron 56. A. C. potential from a suitable source, such as generator 60 is applied to the plate of thyratron 56 when switch 62 of firing relay 20 is closed.

, The closure of trigger switch 18 by the pilot, when he fires his armament, energizes coil 63 of firing relay 20. Relay 20 is of the conventional type which will remain energized a predetermined period of time after switch 18 is closed. The period being selected so that the shutter of-camera 26 will not be operated until after each exposed film has had time to be developed.

In operation, the aircraft 12 is provided with tracer type ammunition so that its position can be easily photographed in daylight. When the pilot sights the target and commits himself to making an attack, he tracks the target. During the period of time that the pilot is tracking the target the computer, in the process of solving the fire control problem, will be deriving the time of flight to the target of the particular missile to be fired. In a preferred type of computer this information is available as the positive D. C. voltage Vtf- A portion of V is picked ofl by potentiometer 36 and applied to the D. C. amplifier 46 through the cathode follower 4t), switch 42 and input terminal 44. When the firing relay 20 is not energized, switches 42, 50 and 62 are in the position illustrated in Fig. 4. Switches 42, 50 and 62 are mechanically linked by shafts 70, which are illustrated as a dashed line, to armature 72 of firing relay 20. Amplifier 46 amplifies the input voltage, and, as a result of the feedback circuits, the output voltage, V the potential at output terminal 48 will be a predetermined function of the input voltage V Current will flow through the negative feedback resistor 52 so that a voltage will exist across it. Condenser 54 charges up so that the voltage across it equals the voltage across resistor .52. The potential at output terminal 48 is suificiently negative to bias thyratron 56 to cut off. Also, thyratron 56 will not be able to conduct until switch 62 closes when timerelay 20 is energized.

When. the pilot presses the firing switch 18, the missiles are ffired, and coil 68 of firing relay 20 is energized. Armature 72 is pulled in'and causes the switches 42, 50 and 62 to change position. Switch 42 now connects a negative voltage V to the'input' terminal 44 from terminal-74 through resistor 76. Negative feedback through resistor 52 stops when switch 50 opens, and condenser 54 begins to discharge through resistor 76. As oondenser 54 discharges, the voltage across it decreases at a constant rate because of the high gain characteristics of amplifier 46 when negative feedback through resistor 52 no longer occurs. The time that it takes for the voltage across condenser 54 to decrease to the voltage at which thyratron 56 conducts is equal to the time of flight t as computed by the computer 10. To do this the location of arm 38 is adjusted so that the desired result is obtained. When the voltage at terminal 48 has risen to the voltage at which thyratron 56 will conduct, the tube 56 conducts because switch 62 closed when coil 68 was energized, and current will flow through the coil 58 of camera relay 22. Relay 22 then causes solenoid 24 to be energized to operate the shutter mechanism of camera 26 at the time when the missles should intersect the target, or the time at which the missiles will pass closest to the target.

Normally the missiles will be fired in bursts, the length of the burst is known approximately so that a fixed additional period of time can be added to the time of flight, tf as computed by computer 10 by adjustment of the potentiometer arm 38, so that the camera shutter will be operated at the time the middle round, or rounds, are passing closest to the target. It is, of course, essential thatthe pilot continue to track the target for a period of time after he ceases to fire his armament which period is equal to the time of flight so that the camera will be pointing in the general direction of the target when the shutter is opened.

Fig. 5 is an example of the type of picture that is made available to the pilot. It shows streaks of light made by the tracer type devices of a plurality of rockets 78 at the time they are passing closest to the target 80. From Fig. 5 the pilot will observe that his rocket passed below and slightly to the right of the target. He should remember what he was doing at the time he made the attack, and before he makes a second attack on the target he will know the direction and magnitude and probable cause of the miss on the first attack. By repeated at tacks and knowing the results of each attack before he makes the next the pilot will in a short period of time learn to use his fire control system and ammunition properly.

In describing the use of the miss-distance indicator reference has been made to a fighter type aircraft firing armament parallel to the flight path of the aircraft. The invention is not so limited, and can also be used for training of gunners of aircraft, for example. The particular type of timing circuit used is a matter of choice, the one illustrated being a preferred model.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the, scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A miss-distance indicator for an aircraft having means for firing. tracer type missiles, comprising in combination, a camera means mounting the camera on the aircraft in proximity with the pilot and so that the camera will take a picture in the direction the armament is fired, a solenoid actuator for opening the shutter of the camera, a camera relay'for energizing the solenoid, a computer for producing a voltage which is a prededermined'function of the time of flight of the missile from the aircraft to the point of intercept with the target, a timer, the voltagefrom the computer being applied to the timer, a firing relay, and a trigger switch, said trigger switch energizing said firing relay when the trigger switch is'close'd, said firing relay when energized causing the timer, after a-period of time, substantially equal to' the time of flight of the missiles to the intercept point with the target, to energize the camera relay, whereby said camera relay energizes the solenoid and causes the film of the camera to be exposed at the time the missiles are closest to the target.

2. In combination an aircraft and a miss-distance determination system therefor, said aircraft including means for firing missiles and fire-control computing means associated with said firing means, said computing means including means for computing the time of flight of a missile from the time of firing to the time of intercept with a target, said miss-distance determination system comprising a camera mounted in said aircraft in a position to take a picture in the direction a missile is fired,

camera shutter actuating means, and means responsive to operation of said firing means to operate said shutter actuating means at said computed time'subsequent' to said operation of said firing means.

6 3. The combination of claim 2 wherein said camera is of the type adapted to produce a positive print shortly after its film has been exposed, whereby a photograph of the fired missile at its nearest point to the target is' made available while the aircraft is still airborne so that further firings may be made immediately to correct for errors in tactics in the earlier firing.

References Cited in the file of this patent UNITED STATES PATENTS 2,283,788 Briechle et al. May 19, 1942 2,346,079 Newton Apr. 4, 1944 2,382,981 Edgerton Aug. 21, 1945 2,408,764 Edgerton Oct. 8, 1946 2,419,978 Wildman May 6, 1947 2,463,233 Alexanderson Mar. 1, 1949 I 

